The goals of the cohort follow-up and database maintenance core (Core A) are to: 1. develop and mail follow-up questionnaires, to process returned questionnaires, verify responses and compile the database of exposure data; 2. to trace lost subjects and maintain their name and address file for the Nurses' Health Study (NHS) cohort. 3. to maintain cohort participation through newsletter, certificate of appreciation and correspondence and reply to queries from participants. Core A, under the direction of Graham A. Colditz, M.D., Dr.P.H., develops and designs the questionnaire for biennial follow-up study participants. This questionnaire design incorporates input from other investigators on the Program Project through the bi-weekly meetings. New questions are pilot tested and follow-up methods are refined to address the needs of the aging cohort members. Returned questionnaires are checked for completeness, optically scanned, and verified for scanning errors. The questionnaires are finally stored on CD-rom. Core A uses a range of methods to trace participants and to maintain high levels of participation. At the completion of the 1996 follow-up cycle, 90 percent of participants responded. The 1998 follow-up cycle is continuing. Core A is responsible for derivation of variables from the questionnaire responses. This included maintaining a nutrient database to derive nutrient values after the completion of food frequency questionnaires (FFQs), the updating of menopause and duration and type of hormones used after menopauses, and the general documentation of the Nurses' Health Study (NHS) database.